chore(deps): do not attempt to update nginx (#2017) (#2018)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Introduced a new configuration file for automated dependency updates,
enhancing version management.
- Implemented specific rules to preserve compatibility with legacy
systems by restricting updates for certain packages.

- **Documentation**
- Updated documentation to clarify the importance of maintaining legacy
dependencies for older clients.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: drazisil

.renovaterc.json5

@@ -0,0 +1,22 @@
+{
+    "extends": [
+        "config:best-practices",
+        ":automergeStableNonMajor"
+    ],
+    "packageRules": [
+        {
+            "allowedVersions": "1.9.8",
+            "matchDatasources": [
+                "docker"
+            ],
+            "matchPackageNames": [
+                // Prevent automatic updates from nginx:1.9.8
+                // While this image can still be found on DockerHub,
+                // it is also archived at https://archive.org/details/nginx_1.9.8.tar
+                // This is required to serve as a proxy to the [SChannel](https://web.archive.org/web/20230402130420/https://learn.microsoft.com/en-us/windows/win32/com/schannel) that Windows XP uses.
+                // Windows XP is required support since the legacy client can not be upgraded or modified.
+                "nginx"
+            ]
+        }
+    ],
+}